Geology 1403 Exam 4

parts of the hydrologic cycle

Precipitation
Evaporation
Infiltration
Runoff
Transpiration (same as Evapotranspiration)
Atmospheric advection

precipitation

the fall of water, ice, or snow from the atmosphere

evaporation

changing of liquid to a gas

infiltration

water soaks into the ground.
controlled by:
-intensity and duration of rain
-soil texture
-slope of the land
-vegetation cover

runoff

part of water that isn't soaked into the ground, moving downward into streams ect.

transpiration

evaporation of water previously absorbed by plants, same as evapotranspiration.

atmospheric advection

horizontal transport of air and atmospheric property

sheetflow

running water begins as _____

rills

sheet flow develops into tiny channels called ____

laminar flow
turbulent flow

two types of flow determined primarily by velocity

laminar flow

low velocity stream
particles are moving along straight line paths, without mixing.

turbulent flow

high velocity stream
particles have multidirectional paths and are mixing

1. gradient-slope inclination
2. channel characteristics such as shape, size, and roughness
3. velocity
4. discharge= channel width x depth x stream velocity

streamflow characteristics include:

base level

lowest point the stream can erode

ultimate base level

the sea level is the ____

1. narrow and straight
2. wide and meandering
3. braided (rare)

general types of stream valleys (3)

abrasion
dissolution

types of stream erosion

1. dissolved loads- Calcium carbonates (CaCO3) and salts (NaCl)
2. suspended load- sand, silt, clay
3. bed load- rock fragments

types of loads (3)

1. traction
2. saltation
3. suspension
4. in solution

types of stream transportation (4)

traction

large rock fragments roll and slide along the river bed

saltation

smaller rock fragments bouncing off the river bed

suspension

mud and silt size particles are carried without any contact with the stream bed

in solution

matter travels in ionic state (invisible)

capacity

maximum load a stream can carry

competence

maximum size particle a stream can move

alluvium

stream sediments that are generally well sorted and rounded: sand and pebbles

bars

channel deposit. most often composed of sand and gravel

delta deposit

forms when a stream enters an ocean or lake, velocity decreases.
3 types of beds:
topset bed- mixture of dif. size particles
foreset bed- coarse particles
bottomset bed- silt and clays, distant from the mouth

point bars

channel deposits formed inside meanders

natural levees

sand bars in the river floodplain formed parallel to stream channel by successive floods over years

narrow stream valley

V-shape, mountains streams, with waterfalls and white waters

wide stream valley

well developed floodplain with meanders, natural levees, oxbow lakes, point bars & cut banks

drainage basin

imaginary line that separates the basins of two neighboring rivers

dendritic
radial
rectangular

common drainage patterns include

dendritic

"tree like" channels. most common

radial

channels radiate outward like spokes of a wheel from a high point

rectangular

channels have right angle bends (characteristic of limetones)

zone of aeration

zone that materials are filled mainly with air

water table

boundary between unsaturated zone above and saturated - below

zone of saturation

all pores and spaces between particles are saturated with water

porosity

percentage of pore space. determines how much groundwater can be stored

permeability

ability of materials to transmit water (connection between pores)

aquifer

permeable rock (sand, gravel)

aquitard

impermeable layer (clay)

- lowering of the water table
- cone of depression in the water table

pumping of wells can cause (2)

artisan well

water rises above the top of the aquifer without any pumping

-subsidence (ground sinks)
-saltwater contamination

Problems associated with groundwater withdrawal (2)

karst topography

landscapes that have been shaped mainly by the dissolving power of groundwater

caverns

formed in limestone (CaCO3) , above water table

Irregular terrain
Sinkhole or sinks
Disappearing streams
Small lakes -sink ponds
Solution valleys
Subterraine caverns

common features of karst topography include: (6)

glacier

thick mass of ice that originates on land from the accumulation, compaction, and re-crystallization of snow. forms when more snow falls in winter than melts in the summer

valley (alpine) glacier

glacier that exists in mountainous areas

ice sheets (continental glacier)

glacier where ice flows out in all directions, creating a dome shape. EX: greenland, antartica

1. plastic flow
2. basal slip

two types of glacier movement:

plastic flow

occurs within the ice. under pressure, the ice behaves as a plastic material

basal slip

entire ice mass slipping along the ground

zone of fracture

from the surface down up to 50 m.
Tension causes crevasses to form in brittle ice

transverse crevasse

forms perpendicular to the direction of the ice movement

longitudinal crevasse

forms parallel to the walls of the glacier valley

zone of accumulation

area where the glacier forms

snowline

outer limits of the zone of accumulation

zone of wastage

area beyond the snow line where there is a net loss to the glacier due to melting and calving

budget of glacier

balance or imbalance between accumulation of ice and loss of ice.

more snow falls in winter than melts in summer - glacier advances/lengthen

less snow falls in winter than melts in summer - glacier retreats/ becoming shorter

melting

occurs at the lower end of a glacier and is the birthplace of a stream

calving

the breaking off of large pieces of ice

plucking

lifting of rocks, by basal part of a glacier

abrasion

scratching and polishing of rocks that produces:

Glacial striations

Rock flour - less

Glacial trough- v-shaped stream valley transforms into a deep u-shaped glacier valley

Hanging valleys- left standing above the main glacier trough. waterfalls are a characteristic

Cirques- bowl shaped depression at the head of the glacial valley

Fiords- deep steep sides inlets of the sea

Arêtes- sinuous sharp-egded ridges

Horns- sharp pyramid- like peaks

Landforms created by glacial erosion: (6)

glacial drift

refers to all sediments of glacial origin

till

material that is deposited directly by the ice. typically unstratified and unsorted

stratified drift

sediments laid down by glacial meltwater = till + imported rocks

depositional landforms

______ are made of till

1. moraines
2. drumlins

two types of landforms made by glacial deposits

moraines

landform that consists of layers or ridges of till

lateral moraine

landform that consists of layers or ridges of till. parallel to valley walls

medial moraine

landform that consists of layers or ridges of till. present in the middle of the glacier

ground moraine

gently rolling layer of till deposited as the ice front recedes

drumlins

streamlined, elongated, asymmetrical hills. steep side faces the direction to which ice advanced

tarns

small lakes in a cirque basin, left by alpine glacier

paternoster lakes

water in a bedrock depressions along the valley

kettle lakes

water in depressions left after continental glacier melts away

kames

small, steep-sided hills

eskers

low, sinuous ridges

Ice-contact deposits

deposited by meltwater flowing over, within, and at the base of motionless ice

1. plate tectonics (large scale: millions of years)
2. Variations in Earth's orbit: shape of the orbit, angle of the axis, and axis wobbling (smaller scale:100,000 years, 410000 years, 23000 years)

causes of glaciation (2)

the milankovitch hypothesis

explains the changes in climate that plate tectonics can't explain

semiarid zones (steppe in asia or Prairie in N and S america)

zone adjacent to deserts with precipitation less than 60 cm per year

Arid zone (called deserts)

zone with precipitation about 50-25 cm per year

Low - Latitude or Trade wind deserts
Midlatitude deserts

two types of deserts classified by location and dominant weather pattern

Low - Latitude or Trade wind deserts

deserts located in the vicinities of the tropics. areas controlled by anticyclones (dry, sunny). EX: Sahara desert

midlatitude deserts

deserts located in the deep interiors of continents. not controlled by anticyclones.

rain shadow deserts

high mountains are in the path of the prevailing winds force the air to rise, it then expands and cools, forming clouds and precipitation. EX: sierra nevada range, Gobi desert

coastal deserts

smaller size desert, no permanent location, generally on the western edged of continents near the tropics, depend on local wind system which makes them less stable than other deserts EX: Namib desert in Africa

polar deserts

precipitation less than 250mm/y. no sand dunes but mostly bedrock and gravel plains

paleodesert

desert of the past. well preserved crescent shape dune EX: Nebraska Sand Hills

mechanical weathering in arid climates

produces unaltered rock and mineral fragments

chemical weathering in arid climates

this produces clay, thin soils, oxidized material

main erosional agent in deserts

role of water in arid climates is the

Wash and arroyo (Western U. States)

Wadi (Arabia and North Africa)

Donga (South America)

Nullah (India)

different names used for desert streams

early stage
middle stage
late stage

Evolution of a desert landscape (3)